An NHS expansion plan for mental health services will see thousands of new posts created, the Government has said.
Health Secretary Jeremy Hunt said the aim was to treat an extra one million people by 2021 under one of the biggest boosts to mental care in Europe.
However, the Royal College of Nursing (RCN) questioned whether enough people could be trained in such time, and if there were the resources to do so.
The £1.3 billion drive will provide services seven days a week, 24 hours a day, and properly integrate mental and physical health services for the first time, Mr Hunt said.
The number of trained nurses, therapists, psychiatrists, peer support workers and other mental health professionals will be "dramatically" increased with 21,000 new posts under the plan, according to the Health Department.
Mr Hunt said: "As we embark on one of the biggest expansions of mental health services in Europe it is crucial we have the right people in post - that's why we're supporting those already in the profession to stay and giving incentives to those considering a career in mental health.
"These measures are ambitious, but essential for delivering the high performing and well-resourced mental health services we all want to see."
Janet Davies, chief executive of the RCN, said: "The Government's policies appear not to add up.
"If these nurses were going to be ready in time, they would be starting training next month. But we have seen that the withdrawal of the bursary has led to a sharp fall in university applications and we are yet to see funding for additional places.
"There is already a dangerous lack of workforce planning and accountability and this report is unable to provide detail on how the ambitions will be met.
"It is clear the Government will need to work hard just to get back to the number of specialist staff working in mental health services in 2010. Under this Government, there are 5,000 fewer mental health nurses and that goes some way to explaining why patients are being failed.
"The NHS needs to see hard cash to deliver any plans."
Professor Wendy Burn, president of the Royal College of Psychiatrists, which helped devise the plan, said: "As medically trained doctors, psychiatrists are vital to the treatment of mental illness. You would expect to see a consultant if you had cancer and the same applies for mental health.
"The 570 extra consultants promised in this strategy will be crucial to delivering the high-quality, robust mental health services of the future."
The move will see 2,000 additional nurses, consultants and therapist posts created in child and adolescent mental health services.
And 2,900 additional therapists will help adult talking services, with 4,800 extra nurses and therapists in crisis care settings.
Retaining staff and encouraging some of the 4,000 psychiatrists and 30,000 trained mental health nurses not substantively employed by the NHS to return to the profession will form a major part of the drive.
Labour's shadow minister for mental health Barbara Keeley said: "The workforce plan provides no real answers on how these new posts will be funded or how recruitment issues will be overcome. And it offers little hope to those working in the sector faced with mounting workloads, low pay and poor morale.
"Time and again the Tories have been warned that severe staffing shortages are affecting patient care. Only this month the Care Quality Commission highlighted staffing levels, in particular the cuts to mental health nurses, as a contributing factor to 40% of mental health services now failing on safety grounds."